add icmp_proxy diagnostic logging on all reply path stages

src/icmp_proxy.c

@@ -91,7 +91,8 @@ static void raw_read_cb(socket_t sock, void* arg) {
     if (icmp_hdr->icmp_type != ICMP_ECHOREPLY) return;
 
     struct icmp_request* r = req_find_by_id(g_icmp_ctx->pending, icmp_hdr->icmp_id, icmp_hdr->icmp_seq);
-    if (!r) return;
+    if (!r) { DEBUG_WARN(DEBUG_CATEGORY_SOCKET, "icmp_proxy: unclaimed echo reply id=0x%04x seq=%u from=0x%08x",
+                          icmp_hdr->icmp_id, icmp_hdr->icmp_seq, from.sin_addr.s_addr); return; }
     DEBUG_INFO(DEBUG_CATEGORY_SOCKET, "icmp_proxy: echo reply id=0x%04x seq=%u from=0x%08x",
                icmp_hdr->icmp_id, icmp_hdr->icmp_seq, from.sin_addr.s_addr);
 
@@ -111,7 +112,9 @@ static void raw_read_cb(socket_t sock, void* arg) {
     memcpy(e->dgram + 16, &icmp_hdr->icmp_seq, 2);
     if (payload_len > 0) memcpy(e->dgram + ICMP_PROXY_HDR_SIZE, payload, payload_len);
     e->len = ICMP_PROXY_HDR_SIZE + payload_len;
-    etcp_route_send(g_icmp_ctx->inst, r->client_node_id, e);
+    int ret = etcp_route_send(g_icmp_ctx->inst, r->client_node_id, e);
+    if (ret != 0) DEBUG_ERROR(DEBUG_CATEGORY_SOCKET, "icmp_proxy: etcp_route_send reply failed: %d", ret);
+    else DEBUG_INFO(DEBUG_CATEGORY_SOCKET, "icmp_proxy: reply forwarded to client %016llx", (unsigned long long)r->client_node_id);
 }
 
 // ====================================================================
@@ -165,6 +168,8 @@ static void client_handle_reply(struct ETCP_CONN* conn, struct ll_entry* entry)
     memcpy(&src_ip,   entry->dgram + 10, 4);
     memcpy(&echo_id,  entry->dgram + 14, 2);
     memcpy(&echo_seq, entry->dgram + 16, 2);
+    DEBUG_INFO(DEBUG_CATEGORY_SOCKET, "icmp_proxy: client got reply id=0x%04x seq=%u from=0x%08x",
+               echo_id, echo_seq, src_ip);
     struct UTUN_INSTANCE* inst = conn ? conn->instance : (g_icmp_ctx ? g_icmp_ctx->inst : NULL);
     icmp_proxy_deliver_reply(inst, src_ip, echo_id, echo_seq,
         entry->dgram + ICMP_PROXY_HDR_SIZE, entry->len - ICMP_PROXY_HDR_SIZE);
@@ -213,7 +218,11 @@ int icmp_proxy_send_to_exit(struct UTUN_INSTANCE* inst, uint64_t exit_node_id,
 int icmp_proxy_deliver_reply(struct UTUN_INSTANCE* inst,
                              uint32_t src_ip, uint16_t echo_id, uint16_t echo_seq,
                              const uint8_t* payload, size_t payload_len) {
-    if (!inst || !inst->tcp_proxy || !inst->tcp_proxy->tun) return -1;
+    if (!inst || !inst->tcp_proxy || !inst->tcp_proxy->tun) {
+        DEBUG_ERROR(DEBUG_CATEGORY_SOCKET, "icmp_proxy: deliver_reply failed — no %s",
+                     !inst ? "inst" : !inst->tcp_proxy ? "tcp_proxy" : "TUN");
+        return -1;
+    }
     struct tun_if* tun = inst->tcp_proxy->tun;
     uint32_t dst_ip = inst->tcp_proxy->tun_ip_addr;
 
@@ -245,6 +254,7 @@ int icmp_proxy_deliver_reply(struct UTUN_INSTANCE* inst,
     e->dgram[0] = 4; memcpy(e->dgram + 1, pkt, pkt_len); e->len = 1 + pkt_len;
     u_free(pkt);
     queue_data_put(tun->output_queue, e);
+    DEBUG_INFO(DEBUG_CATEGORY_SOCKET, "icmp_proxy: reply delivered to TUN id=0x%04x seq=%u", echo_id, echo_seq);
     return 0;
 }